Reforming and Hydrogen Purification System

ABSTRACT

A reforming and hydrogen purification system operating with minimal pressure drop for producing free hydrogen from different hydrogen rich fuels includes a hydrogen reforming catalyst bed in a vessel in communication with a core unit containing a hydrogen permeable selective membrane. The vessel is located within an insulated enclosure which forms an air inlet passageway and an exhaust passageway on opposite sides of the vessel. Air and raffinate pass through a burner within the air inlet passageway, providing a heated flue gas to heat the catalyst to the reaction temperature needed to generate free hydrogen from the feedstock. The burner flue gas flows laterally over and along the length of the bed between the input and output ends of the bed. Hydrogen is recovered from the core for use by a hydrogen-consuming device such as a fuel cell. The remaining unrecovered hydrogen in the reformed gases is contained in raffinate and is used to supply process heat via the burner. The exhaust flue gas and the inlet air supply pass through a recuperator in which the inlet air is heated from the hot exhaust gas. The feedstock input line is also coupled to the raffinate line and the hydrogen recovery line to preheat the feedstock prior to entry into the catalyst bed.

BACKGROUND OF THE INVENTION

The present invention is directed to a steam reformer for producingpurified hydrogen including purified hydrogen for fuel cells.

Purified hydrogen is an important commodity in semiconductor,metallurgical, and chemical processing. It is also highly useful as asource of fuel for fuel cells, which can produce electrical power fromhydrogen. There are a variety of means for producing purified hydrogen.Hydrogen can be liberated from hydrogen-containing compounds such asalcohol by reforming with steam at elevated temperatures over a catalystbed. Since this reaction is endothermic, the heat can be supplied froman external burner, or the heat can be supplied in-situ by mixing someoxygen and partially burning some of the fuel. The former process isgenerally called steam reforming; when air or oxygen is mixed with thefuel to supply heat the process is referred to as autothermal or partialoxidation reforming. Once the reforming process has been completed,substantial percentages of carbon monoxide will exist in the reformedgas; this carbon monoxide may be further reacted in a water-gas shiftcatalyst bed to form hydrogen and carbon dioxide. This lowers thepercentage of carbon monoxide in the reformed gas.

To create high purity hydrogen from the reformed gas mixture, means canbe employed to separate the hydrogen, e.g. via a selective membrane. Thehigh purity hydrogen can then be used in an industrial process, in afuel cell for power generation or other applications requiring purifiedhydrogen. In some cases, hydrogen purification is not used; the reformedgas is sent to a fuel cell after a selective oxidation step to furtherreduce carbon monoxide levels. In the latter case, the reformer willgenerally require dewpoint control, careful attention to prevent highcarbon monoxide levels, and integration means with the fuel cell toreceive the spent gas after much of the hydrogen has been exhausted.

The technology for hydrogen purification is well known, such asdisclosed in U.S. Pat. No. 5,861,137 entitled Steam Reformer WithInternal Hydrogen Purification issued Jan. 19, 1999. The above patentdiscloses a hydrogen purification system and discusses the prior art andthe state of the prior art. The need for a practical reformer, requiringa cost effective design is clear. The patent discloses a method andsystem for partially extracting of a portion of purified hydrogen froman appropriate fuel feedstock of hydrogen containing fuel and using thedischarged raffinate, with a significant amount of hydrogen therein, asthe fuel for operating the burner.

In addition to a significant number of patents, a substantial volume ofother publications are available describing various systems and aspectsof hydrogen purification including systems based on steam reforming.Nevertheless, there is continuing demand for an improved hydrogenpurification system which is cost effective both initially and duringits operating life, as well as readily adapted for efficient and costeffective servicing. There is a particular demand for a reformer with alow pressure drop in the burner air system.

SUMMARY OF THE INVENTION

The present invention is particularly directed to a hydrogenpurification reformer which may be constructed as a compact unit withefficient heating of the reformer from a burner. The burner gas has aminimal pressure drop in the system which results in a low power and lowcost air supply for processing of the hydrogen rich fuel.

The novel reformer system of the present invention includes a catalystunit or bed which is constructed and arranged along the path of afeedstock between a feedstock input and a spaced feedstock output. Thecatalyst is operable upon heating to establish an endothermic reactionon the feedstock to produce hydrogen. The catalyst may be of anyoperative material, in any available form, such as a self supportingmass, a granular mass or combination thereof. If a granular mass isused, a confining enclosure supports the mass with a constructionallowing release of the hydrogen therefrom for subsequent collection viaa hydrogen permeable membrane.

In accordance with a particular feature of this invention, a burner unithas a flue gas output stream communicating essentially directly from theburner unit to the catalyst unit and having a length substantially onthe order of the length of the catalyst unit, i.e. typically the spacingbetween the catalyst unit's outlet and inlet. The flue gas stream thuspasses laterally over substantially the entire length of the catalystresulting in minimal air pressure drop in the system.

A hydrogen collector is located adjacent the catalyst unit to collectthe purified hydrogen, or may alternatively be located downstream in thesame or in a separate pressure vessel. In accordance with currentpractice, the hydrogen collector may include one or more hydrogenselective permeable membrane units located along the path of thehydrogen liberated from the catalyst bed to collect the hydrogen.

The preferred construction particularly provides for the efficientfunctioning of the catalyst and the heating of the catalyst, thefeedstock and the air supply, as well as permitting use of a relativelylow pressure air supply, yielding higher energy efficiency.

This construction thus establishes improved heating of the catalyst toproduce the free hydrogen and the extraction thereof from a catalystunit. This system further permits optimizing the heating pattern of thestream over the length of the bed for the internal processing of thefeedstock, as hereinafter described.

In a preferred construction, a pressure vessel contains a closedhydrogen selective permeable membrane core unit surrounded by a catalystbed or unit. A gas fired heating unit has a flue gas output which isaligned with the pressure vessel and particularly the catalyst unit. Theheating unit creates a flue gas stream related to the length and crosssection of the catalyst unit. The flue gas stream passes laterally overthe catalyst unit to heat the catalyst unit throughout the lengththereof. The catalyst unit may be heated uniformly or may be heated to adesired thermal gradient.

The hydrogen rich feedstock passing through the heated catalyst unit isreformed, producing hydrogen. A substantial portion of this hydrogensubsequently passes through the hydrogen selective permeable membranecore unit, and the remaining hydrogen and other gases, hereinafterreferred to as raffinate, exits the pressure vessel, passes through apressure control device such as a back pressure regulator, and issubsequently is used to supply heat for the reforming process via thegas fired heating unit.

The heating unit is preferably a catalytic burner which is preferablyfueled by the raffinate exiting the pressure vessel. The burner may be aseparate burner or constructed as an integrated part of the pressurevessel. In either construction, the raffinate is mixed with air, travelsthrough the burner, and passes a heated stream of flue gas directly fromthe burner over the pressure vessel.

In either construction, the pressure vessel includes an outer shell orwall which is formed of a heat conductive material. A plurality of heatconductive fins are intimately affixed to the outer wall throughout thevessel, through which the heated burner flue gas passes to thoroughlyheat the reforming catalyst bed contained within the pressure vessel.The pressure vessel is located between and defines an inlet burner fluegas passageway and an outlet burner flue gas passageway.

In a preferred construction, the feedstock is preheated through recoveryof heat from at least one of the purified hydrogen, the raffinate, andthe burner flue gas, and preferably from all three sources. Even if thefeedstock is fully preheated to the desired reaction temperature, theendothermic reaction within the catalyst generally requires anadditional supply of heat such as from the burner flue gas in order tomaintain a sufficient temperature for the desired reforming reactions tooccur.

The pressure vessel is also preferably formed with a hydrogen collectionsystem including one or more collection structures. Each collectionstructure includes an inner membrane core of a porous material with ametallic hydrogen permeable selective membrane affixed to the core thatforms a hydrogen selective core-membrane unit. The metallic hydrogenselective membrane may, for example, be a palladium or apalladium-copper alloy coating, the latter which may be fabricated withplating and annealing techniques familiar to those skilled in the art.In addition, each core-membrane unit is separated and spaced from thecatalyst unit, particularly where a granular catalyst is used, toprevent abrading contact of the thin membrane with the catalystmaterial. For this purpose and particularly where a granular catalyst isused, a guard layer may be placed between the catalyst and the membrane,where the guard is porous or contains apertures for communicating thereformed gases to the hydrogen selective permeable membrane.

The pressure vessel is further formed in the preferred embodiment withan outer closed end and an opposite open end, which may be closed by areleasable cover or header unit. The input and output lines are securedto the cover. The lines include a feedstock line to input the feedstockinto the catalyst bed, a raffinate output line to receive the raffinatefrom the catalyst unit and a purified hydrogen output line fortransmitting the purified hydrogen from the core-membrane unit.

The pressure vessel is typically formed of a metallic alloy. A pluralityof spaced fins, which are also good conductors of heat, are firmlyaffixed to and extend from the pressure vessel. However, in smallerembodiments where the surface-area-to-volume ratio is favorable, thefins may not be necessary for heat transfer into the catalyst area, andthe pressure vessel fins may then be eliminated from the preferredembodiment, with the vessel still defining the air and heating gaspassageway and the exit or exhaust passageway.

The heating system preferably includes a controlled distribution of astream of the burner fluid or flue gas over the catalyst unit to producean optimal reforming of feedstock. This requires a maximum heat input atthe inlet or entrance of the feedstock into the unit with a progressivepatterned reduction or gradient over the length of the unit to theoutlet, since a higher proportion of the endothermic reaction occursnearest the entrance point (the inlet end) into the catalyst.

In accordance with a further aspect of the invention, the burner fluegases, the heated raffinate and the collected hydrogen, all of whichcontain significant levels of heat are used to heat the cold input airto the burner and to preheat the hydrogen rich feedstock prior topassing of the feedstock through the reforming catalyst unit.

In a preferred construction, separate conduits carry the raffinate andthe purified hydrogen as they exit the pressure vessel. The conduitseach include at least in part a metal or other heat transfer materialwhich are coupled and preferably bonded to each other and to acorresponding third metal conduit carrying the feedstock to thecatalytic unit, in counterflow fashion. The several conduits arepreferably coupled to each other by a high heat transfer bonding, as bywelding, brazing or the like, to promote heating of the cold feedstock.Other forms of coupling the conduits may be used.

In addition, in one preferred construction, the flue gas from acatalytic burner unit downstream of the catalyst bed is coupled to anextended length of the input feedstock line, as by locating a coiledlength thereof within the outlet passageway carrying the hot exhaustflue gas. This construction can be used to preheat the feedstock withthe flue gas exhaust, which is particularly advantageous when using acatalytic burner.

In accordance with a further preferred construction, a burner air inletchamber for supplying air to the burner and an exhaust chamber fordischarging of the flue gas from the catalytic unit are located inclosely-spaced side-by-side orientation. A heat recuperator includes atransfer assembly extended between the two chambers to thereby capturethe heat in the burner flue gas and transmit the heat to the burnerinlet air, preferably in a counterflow fashion, prior to exhausting ofthe flue gas from the system. This construction can be used to preheatthe burner inlet air with the flue gas exhaust.

A preferred structure of the heat transfer assembly includes a series ofrelatively thin heat conductive and apertured plates which extendbetween and across the two chambers. The plates are separated by thinthermally insulating separators between the adjacent chambers to preventthe burner flue gas from passing into the air inlet chamber orpassageway. These thin separators may also serve to thermally isolatethe apertured plates from one another.

The reformer apparatus is further preferably constructed by orienting ofthe components in a linear, parallel orientation along a linear axis.The maximum output is thereby related to the proportional linear lengthof the related components, with the catalytic burner area, catalystvolume, and heat transfer surface areas generally remaining constant perunit length of the device.

Thus, the location and structure of the burner, and several heatrecuperating systems have a linear orientation related to the pressurevessel. The capacity of the reforming system is then directly related tothe linear length of the components in the final assembly resulting inefficient and ready scaling of hydrogen generation.

Various monitors may be and preferably are coupled to the fluids withinthe system to control the operation of the reformer.

Various other objects, features and advantages of the invention will bemade apparent from the following description taken together with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings disclose a preferred embodiment of the invention connectedto a hydrogen fuel cell.

In the drawings:

FIG. 1 is a schematic illustration of a steam reformer unit forproducing purified hydrogen coupled to a fuel cell;

FIG. 2 is a pictorial view of a hydrogen purifying unit;

FIG. 2 a is a view of the hydrogen purifying unit of FIG. 2 with apartial removal of the outer walls;

FIG. 3 is a rear perspective view of FIG. 2 a;

FIG. 4 is a rear perspective view of a hydrogen reformer unit shown inFIG. 2 with a reformer vessel unit removed;

FIG. 5 is a perspective view the vessel unit shown in FIG. 4 forreforming of purified hydrogen;

FIG. 6 is an exploded cross sectional view of the vessel unit shown inFIG. 5.

FIG. 7 is a cross section of the vessel unit shown in FIGS. 5 and 6;

FIG. 7 a is an enlarged fragmentary sectional view of parts shown inFIGS. 6 and 7 to illustrate a detail of a sealing unit;

FIG. 8 is a right front perspective view of the hydrogen reformer unitshown in FIG. 4 with the outer enclosure partially removed;

FIG. 8 a is a sectional view of a brazed connection of system fluidlines to preheat the feedstock fuel prior to introduction into thepressure vessel;

FIG. 9 is a left front perspective view of the reformer unit shown inFIGS. 4 and 8, with the outer enclosure partially removed;

FIG. 9 a is a left rear perspective view of the reformer unit shown inFIG. 9;

FIG. 9 b is a cross-sectional view illustrating a parallel heatprocessing input passageway and an exhaust output passageway with theinter-related system components;

FIG. 10 is an end view of a heat transfer and recuperative unit shown inFIGS. 8 and 9-9 b for preheating the air supply to the burner in theinstance where the seal between the plates is only formed in one axis;

FIG. 11 is an enlarged view of a heat transfer plate of FIG. 10 with animproved plate separating structure;

FIG. 12 is a graphical illustration of the heat input to the catalyticbed and the resulting free hydrogen created; and

FIG. 13 is a view of a structure for supplying raffinate to the burnerto provide a dispersed flue gas to the finned pressure vessel.

DESCRIPTION OF ILLUSTRATED EMBODIMENT

FIG. 1 is a simplified illustration of a system for generating purifiedhydrogen from a hydrogen rich fuel source 1 for consumption by device14, which may, for example, be a fuel cell used for supplying electricalpower to a load. The illustrated embodiment of FIG. 1 includes a uniquehydrogen purifier 18 within a suitable support such as outer housing 36,in combination with the associated components.

The system of FIG. 1 includes a steam reformer having a reformerpressure vessel unit 19 which is operable to process fuel/waterfeedstock from a source 1. Although a common pump for the fuel and wateris illustrated for the case where the fuel and water are miscible as apre-mixed feedstock, it is understood that more than one pump may beused for the fuel and water, respectively, along with any needed flowand pressure monitoring means, with the fuel and water streams meetingtogether prior to arriving at the catalyst filled chamber 7. Thepressure vessel unit 19 contains an inner hydrogen purifier core unit18. The pressure vessel unit 19 is larger than the unit 18 and forms thecatalyst-filled chamber 7.

The fuel from source 1 is shown as a mixture of fuel and water andconstitutes a feedstock which is pulled through line 17 to filter 2, andpumped by a pump 3 via a line 4 to the counterflow heat exchanger 9.After receiving heat at heat exchanger 9 the feedstock then receivesmore heat in heat exchanger 5, finally arriving at pressure vessel 19 bymeans of line 6 into pressure vessel inlet connection 60. The feedstockthus is fed into catalyst filled chamber 7, which is heated, ashereinafter described, and the fuel/water feedstock reacts to producefree hydrogen. Unit 18 is an elongate member which contains a specialhydrogen selective permeable membrane, as hereinafter described, whichpasses the hydrogen contained in the reformed gases into the interior ofunit 18, wherein the purified hydrogen is subsequently transferred toline 11 by means of hydrogen outlet 62. While generally illustrated as atubular member the shape of unit 18 is not constricted to any particularform, and can assume any form suitable for the application. Hydrogenpurified by unit 18 and passing through line 11 transmits heat to thefeedstock in heat exchanger 9 prior to passing through hydrogen outputpressure regulator 12. Once the hydrogen pressure has been regulated byregulator 12 the hydrogen may then pass through solenoid valve 13 toconsuming device 14. Since consuming device 14 may consist of a fuelcell with a required periodic bleed, a return line from consuming device14 is included, with passage through bleed solenoid valve 15 and checkvalve 16, where the bleed hydrogen is injected into line 83.

The volume and activity of catalyst 7 and the heating thereof is suchthat the processed fuel is nearly completely steam-reformed by the timeit is withdrawn through line 8.

The remaining fuel and reaction by-products, including unliberatedhydrogen, hereinafter referred to as raffinate, is withdrawn fromcatalyst-filled chamber 7 by a line 8. The raffinate then transmits heatto the incoming feedstock in heat exchanger 9, after which it passesthrough feedstock back pressure regulator 10. The raffinatedepressurizes upon passing through regulator 10 and travels though line83 to burner distributor 21.

A catalytic burner 75 is mounted within outer housing 36 to receiveraffinate from distributor 21 mixed with burner air. The raffinate isdischarged into the air flow via pores or holes in distributor 21, suchas more clearly shown in FIG. 13 for a dual-distributor mechanism. Theair and raffinate are mixed at the input to burner 75 which creates ahot flue gas stream 75 a which passes into the adjacent chamber andfunctions as described above to heat the catalyst filled chamber 7.

The system shown in FIG. 1, provides particular features for improvingthe efficiency and functioning of the reforming process for thegeneration and purification of hydrogen. In particular, the systemprovides various heat recovery from the heated fluids in the lines atheat exchanger 9 and the heated flue gases 78 a which flow downstream ofheat exchanger 5.

As shown in FIG. 1, the portions of lines 4, 8 and 11 are coupled toeach other by a counterflow heat exchange unit 9 which transfers heatfrom the reformed gases back to the incoming feedstock in counterflowfashion. This improves efficiency and also serves to cool the gas priorto arrival at hydrogen output regulator 12 and feedstock pressureregulator 10, protecting the devices from thermal damage. In addition,as also shown in FIG. 1, the line 4 is shown with a coiled heatexchanger section 5 which is in contact with the burner flue gas 79.Heat exchanger 5 is configured to raise the feedstock to the desiredoperating temperature for the catalyst in catalyst-filled chamber 7.Depending on the capacity of the reformer, heat exchanger 5 may includeseveral turns of finned tubing to facilitate heat transfer from flue gas79, or it may consist of an unfinned tube with one or more parallelturns.

Additionally, a heat transfer assembly 30 is located spanning theexhaust chamber 91 and the burner air inlet chamber 90 downstream of fan20 and fan filter 20 a. A backup fan 20 b, as illustrated in FIG. 2 a,may also be used in series with the main fan 20. The hot flue gas 78 aentering assembly 30 raises the temperature of the assembly 30 on theflue gas side which transmits the heat into the cool portion of theassembly 30 on the air inlet in a counterflow fashion. Morespecifically, the assembly 30 is specially constructed to prevent thetransfer of fluids in the respective chambers into the other chamber, asmore fully described in a preferred construction of the system of FIG.1, as shown in FIGS. 2-12, by the use of thermally insulating sealinggasket 97. Insulating gaskets 97 furthermore allow the perforated orexpanded metal plates 96 of assembly 30 to operate at differenttemperatures such that counterflow exchange may be improved.

While the arrangement of heat exchangers regulators, valves, and thelike illustrated in FIG. 1 are specifically shown in a preferredorientation, various arrangements of parts may be employed to achievesimilar results within the framework of the invention, and may bearranged as needed by those skilled in the art.

Referring to FIGS. 2-4, a compact hydrogen source unit 33 includes anouter enclosure wall 34 (partially shown in FIGS. 2 a-4) within which anair supply section 35 is formed across the front wall, and connected toa hydrogen generating unit enclosed in enclosure 36. A control section37 is located to the one side of the air supply section 35 and thehydrogen generator unit in enclosure 36. Section 37 contains variousparts previously described in FIG. 1 such as the pressure regulation andsolenoid valves.

The air supply section 35 includes a housing with an air filter 20 awithin which an air supply fan 20 is located with a backup fan 20 bdownstream of fan 20. As illustrated in FIG. 2 a the backup fan 20 b isan axial type, and the main fan 20 is of a blower type. Fan 20 pulls airthrough filter 20 a and blows it into a housing surrounding backup fan20 b. An air passageway tube 38 connects the output end of backup fan 20b to the hydrogen generator unit in enclosure 36. The outer face of thehousing 35 a is covered by filter 20 a and an outer apertured face cover38 b.

The hydrogen generator unit in enclosure 36 is mounted behind the airsupply section 35 and is surrounded by perimeter insulation 39 restingon a rigid thermally insulating base support platform 39 a. Theinsulation surrounding the high temperature parts contained in enclosure36 permits the efficient operation of the reformer. Specifically this isdone by placing the metallic fastening means to enclosure 36 at thelowest temperature portion of enclosure 36. This includes the airpassageway tube 38, and the top of unit 33 in FIG. 2, to which enclosure36 is fastened. This permits structural attachment of enclosure 36 tothe rest of device 33 while minimizing thermal losses. The input of theair to the generating unit in enclosure 36 is via the air passagewaytube 38. It should be noted that the perimeter wall insulation 39 isonly partially shown for clarity of illustrations and understanding ofthe processing of the air and heating fuel system of the preferredsystem.

Referring to FIGS. 4-8, the pressure vessel unit 19 of FIG. 1 is shownin a preferred finned construction and identified hereinafter aspressure vessel 40. The pressure vessel 40 includes an outer shell orcontainer 42 within which an inner purifier core unit 41 which iscentrally located and secured. In the preferred embodiment, a separatecup-shape guard member 51 is secured between the outer shell orcontainer 42 and the purifier core unit 41. The guard member 51 isspaced from the container 42 and forms a catalyst chamber 7 and is alsospaced from the core unit 41 to prevent abutting engagement of agranular catalyst 50 in chamber 7 with the core unit 41.

In particular, the container 42 includes an outer tubular wall 45, openat both ends prior to assembly. The outer end is closed by a flat endwall 46 welded with weld 47 a (47 a denoting all welds in FIGS. 6 and 7)to the tube 45 and spaced from the inner ends of the cup-shaped guardmember 51 and purifier core unit 41. The opposite or inner end of thetube 45 is closed by a header unit 46 a including a flange member 47secured to the open end of the tube 45, as by a weldment 47 a. Headerunit 46 a is bolted with bolts 53 in a sealed connection using copperseal ring 52 a to the flange member 47. The guard member 51 and thepurifier core unit 41 are secured to the header 46 a to form a removableunit relative to the flange 47 and the outer shell 45 or container 42.Cover 64 is also attached to the flange 46 a via bolts 53.

The cup-shaped guard member 51 is formed of suitable perforated metal orother suitable material to confine the catalyst 50 and to permit freepassage of the hydrogen as well as other gaseous material. The open endof the guard member 51 is secured to the header 46 a by welding or otherconnecting means.

The purifier core unit 41 is formed of a porous ceramic body 41 a withan outer hydrogen permeable metal coating 41 b, with presently knownmaterials such as palladium or a palladium copper alloy coating, forminga hydrogen selective membrane, and thus a hydrogen purifier core unit41. The reformed gases pass freely through the guard 51 into the coreunit 41. The hydrogen gas only passes into the inner collection chamber41 c of the core unit 41 as a result of traversing the outer hydrogenselective membrane 41 b. The guard 51 may take the form of a porouswall, an apertured wall or even a tubular member directing the freehydrogen toward the end thereof, with the hydrogen dischargingtherefrom, into the membrane unit. Where the catalyst is in the form ofone or more monolithic catalyst elements or units mounted in spacedrelation to the selective membrane unit or units, the guard 51 may notbe necessary.

Referring to FIG. 7 a, the flange 47 is recessed and telescoped over theouter end of the tube 45 and is welded to the exterior of the tube 45 asat 47 a. The header 46 a is bolted to the flange 47 with a high pressuresealed gasket 52 a therebetween. The illustrated sealed joint (FIG. 7 a)includes a copper seal ring 52 a located between the flange 47 andheader 46 a. A sharp sealing edge 52 c projects outwardly from 47 and 46a into embedded engagement with the copper ring 52 a upon tightening ofthe securement bolts 53. The seal establishes a high pressure closure toconfine reformed gases within vessel 40. Other suitable seals may beused in the preferred system, and in other systems may be constructedwithout a removable cover structure. For example, end piece 46 a may bewelded or brazed to the end of tube 45 for a permanent closure ofpressure vessel 40.

The input/output lines are sealed within header 46 a and are coupled tothe several passages within the core unit 41 and catalyst chamber 7 ofthe illustrated embodiment, as follows.

A feedstock fuel line 60 is secured in sealed relation to the header 46a. The fuel line 60 extends inwardly into the catalyst-filled chamber 7,and through the catalyst 50 to the inner end portion of the chamber. Theinner end of line 60 terminates, close to the end wall 46 to feed thehydrogen rich feedstock fuel into the closed end of the catalyst filledchamber 7, under appropriate pressure, to move the feedstock axiallythrough the catalyst 50 toward the header 46 a. An alternate arrangementwithin the scope of this invention (not shown) utilizes a feedstockdelivery tube 60 and a raffinate exit tube 63 which extends the lengthof catalyst bed 7, where the tubes are closed at the ends andperforated, such that the gas flows between the perforated tubes ratherthan down the axial length of the catalyst bed. Other arrangementswithin the pressure vessel apparent to those skilled within the art canbe implemented as well.

A hydrogen recovery line 62 is secured within the header 46 a andterminates at the inner core chamber 41 c of core unit 41 and serves torecover the free hydrogen which has passed through the membrane 41 b ofpurifier core unit 41.

A raffinate line 63 is secured to the header 46 a in alignment with thelower or bottom side of the catalyst chamber 7. The pressurizedfeedstock passes through the catalyst 50 and exits as raffinate throughthe raffinate line 63 under pressure. The raffinate generally contains asignificant level of hydrogen and functions as a fuel for the catalyticburner in the air passageway, as hereinafter described.

The raffinate at the outlet of the catalyst, downstream of the purifierunit 41, can provide a fuel to a catalytic or other burner unit.Unreformed fuel, unrecovered hydrogen, and side-reaction products suchas carbon monoxide or methane can serve to function as a fuel in acatalytic or other burners. The particulars of gases contained in theraffinate depend upon the fuel type, steam-to-carbon ratio, pressure,catalyst type, flow rate, and temperature, and may also vary dependingon the time on stream of the catalyst. The reformed feedstock withhydrogen removed by purifier 41 is generically identified herein asraffinate, which will cover all reformed feedstock exiting a catalystunit and a hydrogen purification unit and coupled to the system burner,as disclosed herein, as well as such fuel when combined with or replacedby a separate fuel source.

The container 42 and particularly the tubular wall 45 has spaced andheat conductive fins 59 intimately secured, as by brazing or other highheat transmitting connection, to the container wall 45. The fins 59 areshown as rectangular members which are shaped and formed to fit withinthe corresponding opening in the enclosure for optimal heating of thecatalyst and generation of purified hydrogen, as hereinafter described.The fins 59 are spaced, with size and positioning selected to providerapid heating of the vessel, while yielding a minimal pressure drop forthe laterally passing flue gas flow. The fins 59 are preferably formedof a suitable material such as copper for rapid heat transfer to thevessel, and particularly to catalyst 50.

The pressure vessel 40 (FIG. 4) is removably secured within an opening65 in the enclosure 36 by a plate 64 secured to the header 46 a and tothe enclosure frame structure by attachment screws 65 a. The finnedvessel 40 is enclosed within an internal wall structure to define anair/fuel inlet passageway and an outer exhaust passageway, ashereinafter described.

The finned pressure vessel 40 and particularly purifier core unit 41thereof may require replacement in the event that a breach or otherdegradation of membrane 41 b occurs, or if the catalyst activitydeclines significantly due to coking, poisoning, aging, or otherreasons. The other components are expected to have a long life.

As shown, the finned pressure vessel 40 is removable as a unit. Theillustrated header 46 a may be released from flange 47 and replaced by anew header with a new core unit and guard unit within the finnedcontainer 42. The catalyst may also be replaced during this operation,which is particularly straightforward if the catalyst is formed as amonolithic annular piece rather than the granular material illustratedas 50. The illustrated unit thus provides for a low cost replacementpurifier 41 and pressure vessel 40 for simple serviceability and longlife operation of the reformer.

The feedstock feed line 60, the hydrogen (H₂) recovery line 62 and theraffinate line 63 are secured to header 46 a in spaced relation forinputting the feedstock and withdrawing the purified hydrogen and theraffinate, relative to container 42, as shown in FIGS. 8 and 9. Eachline is similarly constructed with a like line coupling unit 67 whichmay be released and later re-sealed when servicing the unit.

The raffinate line 62 additionally may have a larger releasable coupling68 between header 46 a and the coupling 67 to open the line 63. Thisprovides convenient means for replacing the granular catalyst 50, as maybe periodically required. As previously mentioned, when the catalystconsists of one or more monolithic members, header 46 a must be removedto replace the monolithic catalyst, in which case coupling 68 becomesunnecessary.

The pressure vessel 40 is removably mounted within the enclosure 36, asshown in FIGS. 4, 8 and 9-9 b by fastening screws 65 a. The housingenclosure 36 further contains a variety of interior walls and flowdirecting means to channel the heating gases through the enclosure. Asbest shown in FIG. 9 b, an upper vertical divider wall 69 divides theair inlet plenum 90 from the exhaust gas plenum 91, extending betweenand abutting recuperator assembly 30 and the top of enclosure 36, aswell as the sides of enclosure 36 to form an effective barrier betweenplenums 90 and 91. Below the recuperating assembly 30, rigid thermallyinsulating vertical divider wall 70 further separates the gas flow.Vertical wall 70 abuts and seals to rigid thermally insulatinghorizontal wall 71. Horizontal wall 71 contains an opening 74 permittingthe mixed air and raffinate to flow into catalytic burner 75; otherwisehorizontal wall 71 abuts and seals against the outer enclosure 36 andvertical wall 70 to prevent the flow of gases elsewhere. Horizontal wall71, in combination with the bottom and sides of enclosure 36 and thespaced fins 59 of vessel 40, forms a passageway 74 b for flue gas 75 afor heating fins 59 and the interior of vessel 40. Downstream of vessel40, vertical flue gas divider wall 73 formed of rigid thermallyinsulating material, abutting and sealing against wall 71 and sides ofenclosure 36, directs the flue gas through passageway 76 in its opening78. Wall 73 and the enclosure 36 further define a vertical passage wayfor flue gas 79, containing heat exchanger 5.

Heat exchanger 5, illustrated as several coils of finned tubing (FIGS. 9a and 9 b) is connected within the feedstock line 60 which is connectedto the incoming feedstock line 4 to the catalyst bed, as hereinafterdescribed. The finned tubing 5 is located in that portion of exhaustingflue gas 79 passing therethrough and is effective for preheating thefeedstock in heat exchanger 5 prior to its sequential introduction intoline 6, connector 67, and line 60 arriving at the catalyst 50.

Referring to FIGS. 1, 4, 8 and 9, the raffinate supply connection fromthe reformer vessel 40 to the burner 75 is illustrated, with the linescoupling for preheating the feedstock. Raffinate line 63 exits vessel 40through coupling 68 and 67 to raffinate line 8 (FIG. 1). Raffinate line8 passes through heat exchanger 9, and then into control section 37containing feedstock/raffinate back pressure regulator 10. The backpressure regulator 10 depressurizes the raffinate where it then isallowed to combine with fuel cell bleed hydrogen before arriving atburner feed line 83. Burner feed line 83 then passes into enclosure 36to the burner distributor. An illustrative burner distributor is shownin FIG. 13 showing a tee fitting 86 and two perforated distributors 85and 85 a. 85 and 85 a are shown in FIGS. 9, 9 a, and 9 b as well, wherethey are positioned to mix the raffinate with the incoming burner airprior to arrival at burner 75.

Each tube 85-85 a is hollow and sealed at the outer most ends. Each tube85-85 a is preferably a porous or perforated material, such as a ceramicmaterial, a sintered metal, or perforated tubing or other likefunctioning material. At the start of the system operation, the inletair 74 a in passageway 74 is relatively cold air and the raffinatecannot be generated until the catalytic bed is at a temperaturesufficient to process feedstock. To initiate the bed activation, and topreheat the burner 75 to a temperature sufficient to allow for catalyticcombustion of raffinate, an auxiliary heating source is normallyrequired during start-up. An electrical heater 88 is shown mounted(FIGS. 9-9 a) above the burner 75. The heater 88 is turned onautomatically during the start up of the system to heat the inlet airsupply to the temperature necessary for raising the catalytic burnertemperature to the “light-off” temperature, and the catalyst bed to atemperature sufficient to reform the fuel. Once this temperature isachieved the pump 3 may start pumping feedstock into the device,resulting in generation of the hydrogen freeing reaction in the catalyst50 and the subsequent raffinate fuel for firing of the burner 75. Foralcohol based feedstock, the necessary catalyst bed temperature is onthe order of 250-500° C., depending on the fuel and catalyst choice, andthe catalytic burner light-off temperature for hydrogen in the raffinateis above approximately 100° C. After the “light-off” state isestablished at the burner, the heater 88 for heating of the inlet airsupply may be terminated because the raffinate entering the burner 75 isthen adequate to maintain the proper heating of the catalyst. Thepreheating of the feedstock as described in the preferred construction,further maintains the proper reactance in the catalyst without anauxiliary heat source after light-off.

The raffinate (FIGS. 9 and 9 b) is mixed with the air flow in the airinlet passageway 74 and the mixture passes into and through the burner75 which burns to form high temperature fluid or flue gas 75 a. The fluegas 75 a flows directly into the inlet passageway 74 b, to and overpressure vessel 40 as shown in FIGS. 4, 8 and 9 b. The heated flue gas75 a passes through the fins and over the container 42 of pressurevessel 40 as the only exit from the supply or inlet passageway 74 b. Thefins 59 are suitably spaced transfer the heat into the pressure vessel40 to heat the catalyst 50 and thereby generate the hydrogen for capturewithin the core unit 41. Although the feedstock is preheated, aspreviously described, the reforming reactions requires the additionalheat input from the burner to compensate for the endothermic reaction toproduce hydrogen.

The heating of the catalyst 50 may include special distribution on theaxis of the bed or catalyst unit. An optimal heat distribution curve 100and a resulting reaction curve 101 are shown in FIG. 12. The heatdistribution curve 100 is high over approximately the first half of thecatalyst 50 and then gradually decreases to a low level adjacent theexit or discharge end of the catalyst, since the bulk of the endothermicreaction occurs at the beginning of the catalyst bed. The resultingreaction curve 101 for generating the free hydrogen includes a rapidincrease in the hydrogen over the high heat input portion and thenlevels off to a slight release curve to the exit or discharge end of thecatalyst 50.

Since the heating requirements are higher at the beginning of thecatalyst bed, a higher heat flux is desired in this region compared tothe exit of the catalyst bed. This can be accomplished by decreasing thespacing of the fins nearer the feedstock inlet, or by increasing thetemperature of flue gas 75 a at the nearer the feedstock inlet, or acombination of both.

FIG. 13 illustrates a special construction of the raffinate input to theburner 75 for the optional heating distribution of the vessel. Theraffinate distribution holes in 85 and 85 a are varied to supply aricher raffinate/air mix nearer the feedstock inlet end of the catalystbed 7, while the exit ends of 85 and 85 a have fewer holes, providing aleaner raffinate/air mix. The richest and therefore hottest flue gas istherefore applied at the entrance end of the catalyst bed 7 and theleanest and therefore coolest flue gas at the exit end of the bed 7,generally in accordance with the illustration.

In an alternate configuration the catalytic burner may reside on thesurface of the vessel or on the fins secured to the vessel. Methods forforming catalytic surfaces via methods of coating are known to thoseskilled in the art and are not discussed in further detail. If thecatalytic burner is coated on the fins, the fins are preferably closelyspaced throughout the length of the catalyst unit. This is necessary toinsure that un-burned raffinate does not slip past the fins and flowinto the exhaust passageway 76 with the exiting flue gas 79. In thiscase it is also preferable to use the graduated burner diffuserillustrated in FIG. 13.

A preferred feedstock heat exchanger illustrated as finned unit 5 isshown in FIGS. 4, 8 and 8 a. The lines 8 and 11 exiting vessel 40 viacouplings include lengths of bare metal tubes which are assembled with ametal tube of cold feedstock line 4 in positive abutting engagement. Thebare metal tubes are held in abutting and heat transfer engagement by asuitable coupling, preferably by a heat transfer bond; for example,brazing or welding the three tubes to each other throughout asubstantial length as at 84 c, or otherwise similar by connecting thetubes with other heat-transmitting and bonding materials. The bondedtubes 4, 8, and 11 may be covered by an outer wrap of an insulatingcloth 84 b over the bonded tubes. The bonded lines are assembled in acounterflow assembly with the coldest end of the feedstock line 4abutting the coldest ends of lines 8 and 11. This serves to minimizeheat losses, increasing the efficiency of the reformer. The heatexchanger 5 also serves to cool the hydrogen and raffinate prior toarriving at regulators 12 and 10, respectively, preventing overheatingof the regulators and allowing for a lower cost, lower operatingtemperature regulator.

The bonded lines 4, 8, and 11 are shown in U-shape configuration withequal side ends to create an extended length. The overall length of thelegs is related to and generally corresponds to the length of vessel 40and the inner core unit so that the heat exchanger unit is sized orscaled to the system size with the vessel 40 and the inlet and exhaustas well as for system scaling as hereinafter discussed.

This also provides a relatively simple but highly effective system forheating of the feedstock. Other systems of coupling the lines to eachother may be used. As a result of the recovery of heat and preheating ofthe feedstock, the required heating of the catalyst bed for effectivegeneration of purified hydrogen is reduced, and the counterflowarrangement of the heat exchanger increases efficiency.

As shown in FIGS. 8-9 b, the air inlet plenum 90 is formed to one sideof wall 69 and extended over one half of the top of enclosure 36.Similarly, the other half of the top of enclosure 36 contains exhaustchamber 91 to the other side of the dividing wall 69. Ambient air fromfan 20 arrives in plenum 90 through air inlet 38, and exhaust leavingplenum 91 exits via exhaust aperture 92.

In accordance with the preferred construction and as shown in FIGS. 1and 8-9 b, a heat recovery structure 30 couples in counterflow fashionthe heat in the exhaust flue gas 78 a to the air arriving through airinlet 38 as follows.

The air inlet chamber 90 of FIGS. 1, 8 and 9 is connected to the airsupply tube or passageway 38 shown in FIG. 2 a-3. The exhaust chamber 91includes the exhaust opening 92 in the rear structural wall, as shown inFIGS. 3, 8 and 9 b.

A multiple plate assembly 30 is secured below wall 69, spanning theinlet air and exhaust flue gas streams.

FIGS. 10 and 11 are enlarged pictorial views of the heat transfer plateassembly 30 with enlarged plates 96 for clearly illustrating onepreferred construction of the heat recuperating system for heating theincoming air supply. The multiple plate assembly 30 includes a pluralityof heat transfers plates 96 separated by heat insulating and fluidclosing wall gasket members 97 which maintain separation of the incomingair with the exiting flue gas, while allowing the plates 96 to passthrough and span the incoming air and exiting flue gas regions. Theplates 96 may be formed as like plates of a suitable metal such ascopper, aluminum or other materials which are a good heat transmittingmaterial. The illustrated diamond shaped openings 96 a, or any othershaped openings may be formed in the metal plates. The openings need nothave the same shape or size, nor are the openings in the adjacent platesnecessarily aligned with each other. The size and frequency of theopenings in the plates is scaled sufficient to allow for easy passage ofthe air and flue gas with a minimal pressure drop in the respective gasstreams. The openings also allow for a high surface area fortransferring heat into and out of the plates.

The plates 96 and wall members 97 are preferably thin elements.Typically, the plates 96 have a thickness of 0.005-0.100 inches, andmore preferably 0.020-0.05 inches. The thickness of the plates is scaledsufficient to yield a low temperature drop while transmitting heat fromthe flue gas to the incoming air, and depends somewhat on the metalsused and the desired heat flux needed through the plates. The separatingwall members 97 may have a similar thickness or may be thicker than theplates if desired. The insulating properties of the members 97 arechosen to sufficiently thermally isolate adjacent plates 96; this allowsfor plates to operate at different temperatures thus permittingcounterflow heat exchange between the two gas streams. The lowest plate,in contact with the hottest flue gas 78 a, is therefore at the highesttemperature, while the highest plate, in contact with the incomingambient air, is at the lowest temperature.

As illustrated in FIG. 10, the separating wall member 97 does notencourage parallel alignment of plates 96 in recuperating assembly 30.For this reason, member 97(a) is augmented with extending legs 97 b asshown in FIG. 11. Stacking of a plurality of members 97 and 96 to formassembly 30 thus forces parallel alignment of plates 96.

Although not illustrated, other embodiments of counterflow heat exchangeelement 30 are possible. For example, in an annular arrangement sealingmember 97 becomes donut-shaped, and extending legs 97 b are no longerrequired to yield a parallel orientation of plates 96, where the platesextend between an inner and outer annulus for heat transfer. In yetanother configuration, two separate perforated plates may be folded intoa serpentine pattern, yielding parallel plates. These two pieces may bebrazed together with a thin piece of metal which serves as divider 97.One serpentine assembly of parallel plates would extend into the airplenum, while the other would extend into the flue gas plenum, and theheat transfer between plenums would occur at the brazed joint over thesingle metal divider 97. Other additional variations may be obvious tothose skilled in the art.

In summary, the illustrated embodiment discloses a preferredconstruction for preheating the supply input air which is supplied toburner 75. A practical assembly only needs to include plates or otherelements which provide effective heat transfer of the heat in theexhaust gas to the inlet air via mounting of the elements in sealedrelation within a separating wall; within the broadest aspect of thepresent invention.

The construction for the recovery of the heat in the exhaust gas shouldinclude the relatively large cross-sectional flow areas of the chambersand the associated air and exhaust passageways as well as relativelylarge openings within the heat transfer plates or other heat transferelements forming like large openings such that the structure creates alow pressure drop, and a resulting low power consumption to supply airthrough fan 20.

Like consideration is given to the passageway associated with theheating of the pressure vessel 40. Thus, the catalytic burner 75preferably has a relatively large cross-section and is formed with asubstantial plurality of like parallel passages in the direction of theair/fuel flow therethrough.

For example, a two-inch deep burner having passages on the order of 200cells per square inch and of an extruded ceramic with a precious metalcoating is one example of a higher satisfactory burner, in accordancewith known construction. The recuperator for heating the input air maylikewise be formed from aluminum in an expanded and rolled pattern withan open area approaching 40%.

The pressure vessel 40 is similarly and preferably constructed with arelatively large finned construction and with proper spacing of the finsto establish a low system pressure drop in the gases passing over thevessel, as is heat exchanger 5.

The other heat recovery systems such as the preheat of the feedstockfuel and the recovery of the heat from the purified hydrogen and thereformed gases within the system also provide significant results inproducing an efficient and improved reforming apparatus.

The combined structure with the special air and fuel supplies includingthe heat exchanges at the air inlet and exhaust passageways, thefeedstock preheat coil, the coupled flow lines, the catalytic burner andthe finned pressure vessel may yield a significantly low burner gaspressure drop. As a result, the electrical power requirement for movingof the air and flue gases into and through the unit is low. This, incombination with low thermal losses, yields a corresponding increase inreformer efficiency.

The unique characteristic of the illustrated design also allows for costeffective scalable construction of the systems with different maximumoutput levels. The several components and parts of the illustratedembodiment with the linear axis permits construction of the vessel ofdifferent capacity by designing the linear length of the components tobe directly related to the desired capacity. Thus, each of theinteracting components including the burner area, heat exchange area,the catalyst volume, purifier membrane area, the exhaust heat transfersystem, the counter flow heating unit coupling the feedstock line to theraffinate line and/or the hydrogen line are directly related to thelength on the linear axis of the elements and components and thereforethe final structure, as disclosed herein.

For example, if the length of the pressure vessel is doubled, thelengths of the air and exhaust chambers, the inlet air supply andfeedstock heat transfer units, and the burner and related passagewaywill double, producing a doubled output capacity.

The design and structure of the device is particularly unique inallowing for the ease in scalability, but also provides a cost effectiveservice construction. In the purifier, the membrane and catalystcomponent may require periodic replacement and is readily replaced inthe preferred embodiment. Service in the field may thus consist ofsimply and easily replacing the entire finned pressure vessel containingthe purifier unit and catalyst, or replacing the guard and core unit asattached to the header while reusing the finned vessel and flange unit.

The illustrated embodiment may process any of a variety of feedstocks.Although illustrated in the preferred embodiment using a misciblewater/fuel feedstock, separate fuel and water supply means may beemployed, for a variety of fuels, and which may include various othersteps such as fuel desulphurization, water conditioning, and the like,in accordance with typical feed conditioning steps as disclosed in theknown art. Likewise, the size and placement of the various componentsmay be varied in keeping with the present disclosure. For example,improvements in membrane technology will allow for a much smallermembrane collector area, and similar improvements in catalyst may allowfor a smaller catalyst volume.

The specific monitoring, operation, and control of the reformer, withthe typical user interface requirements such as LCD display 22 andoperator controls 23 (see FIG. 2), involve devices, hardware, operatingstates, and algorithms previously disclosed and known to those skilledin this art. A typical example can be found in “PC-25 C On-Site FuelCell Power Plant Service Manual Volume 1”, ONSI Corporation (April1996), and the like.

In summary, the present invention provides an improved and uniquereformer structure for generating of purified hydrogen from the variousfuels containing hydrogen. The illustrated preferred embodiment of theinvention also provides a reforming system which is operable with a lowpressure drop in the air supply system, with a resulting cost effectivesystem.

1-50. (canceled)
 51. A counterflow heat recuperating system for heatingof an inlet air supply in a reformer for producing hydrogen having anair inlet chamber and adjacent exhaust flue gas outlet chamber separatedby a common wall, said recuperating system comprising a plurality ofheat transmitting plates formed of thermally conductive material, eachof said plates transversely mounted on said vertical wall and extendingacross said air inlet chamber and said exhaust flue gas outlet chamberand including a plurality of distributed openings to permit essentiallyfree inlet air flow and exhaust flue gas flow through said plates, andsealing means between said plates and said common wall to prevent mixingexhaust flue gas and inlet air gas streams, whereby said platesfacilitate the flow of heat from the exhaust flue gas stream to theinlet air supply.
 52. The system of claim 51 where said sealing meanscomprises a thermally insulating sealing member placed between each ofsaid plates, and where the sealing member is of sufficient width tosubstantially prevent mixing of the inlet air and exhaust flue gas. 53.The system of claim 52 wherein each of said heat transmitting plates islocated in a plane perpendicular to the flow of said inlet air supplyand said exhaust flue gas. 54-55. (canceled)